ATOMS AND THE PERIODIC
TABLE
chapter three
3.1 Atomic Structure
ATOMIC THEORY - history
4TH CENTURY
B.C.
Matter is made of tiny
particles called ATOMS.
John
DALTON
EARLY 1900’s
(1913)
MID 1900’s
Modern
(after 1925)
theory
ELEMENTS are made
of particles called atoms.
ATOMS of the same
elements are alike.
ATOMS form molecules.
ELECTRONS orbit like
planets in the solar system.
3.1 Atomic Structure
ATOMIC THEORY - STRUCTURE
MODEL OF THE ATOM
ENERGY
LEVELS
ELECTRON
-
NUCLEUS
PROTON
+
NEUTRON
(NEUTRAL)
3.1 Atomic Structure
ATOMIC STRUCTURE
ELECTRON LOCATION
Electrons are found in energy
levels of an atom.
Electrons occupy the lowest
energy level available.
3.1 Atomic Structure
Energy Levels are like ladder rungs…
GAINING
ENERGY
3.1 Atomic Structure
Energy Levels
3.1 Atomic Structure
ORBITALS – where the electrons
are located within an energy level.
S orbital
(Like a sphere)
may contain up to 2
electrons
first energy level is an
s orbital
3.1 Atomic Structure
P orbital
(Like a dumbbell)
may contain up to 2
electrons
second energy level
may contain an s
orbital and up to 3 p
orbitals
3.1 Atomic Structure
Orbitals
3.1 Atomic Structure
Valence electrons are located in the
outermost energy level of an atom.
They determine the chemical
properties of an element.
3.2 A TOUR OF THE PERIODIC
TABLE
• Properties of elements change in a regular
pattern that the table helps to describe.
• Periods – Horizontal Rows
• Groups(families) – Vertical Columns
3.2 Guided Tour of Periodic Table
Traditional Periodic Table
3.2 Guided Tour of Periodic Table
The number of protons in an atom
determines an element’s location
on the table.
3.2 Guided Tour of Periodic Table
Elements On the Periodic Table
ATOMIC
NUMBER
6
PROTONS
(and ELECTRONS too)
SYMBOL
NAME
MASS
C
Carbon
12.001
PROTONS
+ NEUTRONS
MASS #
3.2 Guided Tour of Periodic Table
1
1
PROTONS AND NEUTRONS
HAVE EQUAL MASS.
ELECTRONS ARE TINY – 1800
EQUAL ONE PROTON.
1800
1
3.2 Guided Tour of Periodic Table
MASS
ATOMIC NUMBER
35
17
Cl
protons _?_ electrons _?_
neutrons _?_
3.2 Guided Tour of Periodic Table
MASS
ATOMIC NUMBER
35
17
Cl
protons 17 electrons 17
neutrons 35-17 = 18
3.2 Guided Tour of Periodic Table
IONS are atoms that have lost or
gained an electron.
• ELECTRON GAINED =
NEGATIVE CHARGE
(-)
ELECTRON LOST =
POSITIVE CHARGE
(+)
3.2 Guided Tour of Periodic Table
Electron
transfer
Na+
Cl
3.2 Guided Tour of Periodic Table
TWO KINDS OF IONS:
A (+) CHARGED
ION IS A Cation.
A (-) CHARGED
ION IS AN Anion.
EXAMPLES:
• LITHIUM
• FLUORIDE
3.2 Guided Tour of Periodic Table
The atoms of an element always
have the same number of protons.
BUT…..
The atoms of an element may have
different numbers of neutrons.
This is an ISOTOPE!
Two carbon ISOTOPES:
CARBON 12 = 6 protons and 6 neutrons
CARBON 14 = 6 protons and 8 neutrons
3.2 Guided Tour of Periodic Table
The AVERAGE MASS of an ATOM
• Why is the mass number not an even
number?
– Atoms of the same element exist with
different numbers of neutrons.
– This makes the mass of different atoms of
the same element different.
– The average mass is a weighted number so
that more common isotopes have a greater
affect on the average than rare isotopes.
• What is an amu?
– It is an “atomic mass unit”.
– An amu is equivalent to the mass of 1/12 of
a carbon-12 atom.
3.3 FAMILIES OF ELEMENTS:
• HAVE THE SAME VALENCE NUMBER.
• HAVE SIMILAR CHEMICAL AND
PHYSICAL PROPERTIES.
• A COLUMN OF ELEMENTS IS A
FAMILY.
3.3 Families of Elements
TWO MAJOR DIVISIONS
• METALS
• NONMETALS
3.3 Families of Elements
GROUP ONE:
ALKALI METALS
• VERY REACTIVE
• ONE VALENCE
ELECTRON
3.3 Families of Elements
GROUP TWO:
ALKALINE EARTH METALS
• TWO VALENCE ELECTRONS
3.3 Families of Elements
GROUP 3-12:
TRANSITION METALS
• MANY COMMON METALS
• NOT AS REACTIVE AS OTHER
METALS
3.3 Families of Elements
GROUP 17:
HALOGENS
• VERY REACTIVE
• FORM SALTS WITH ALKALI METALS
• 7 VALANCE ELECTRONS
3.3 Families of Elements
GROUP 18:
NOBLE GASES
• INERT / UNREACTIVE
• EIGHT VALENCE ELECTRONS
3.3 Families of Elements
SYNTHETIC ELEMENTS
• They are man-made and radioactive.
• They include all elements above #92, plus
#43 and #61.
3.3 Families of Elements
SEMICONDUCTORS (METALOIDS)
The elements that are between the metals and
nonmetals are known as:
SEMICONDUCTORS (METALOIDS)
They may exhibit metallic and nonmetallic
properties.
B
Si
Ge
As
3.4 USING MOLES TO COUNT ATOMS
• Some counting units:
–
–
–
–
Reams of paper
Dozens of eggs
Atomic mass units of protons and neutrons
Moles of atoms
• A mole is the SI unit that describes the amount of a
substance.
• Avogadro’s constant is the number of particles in
one mole which = 6.022 x1023
• molar mass is the mass in grams of one mol of a
substance…it is equal to the average atomic number
of an atom.
Chapter 3
Studying for the Test
•
•
•
•
•
•
Vocabulary
Parts of an atom
History
Element families
Using the periodic table
Metal vs. nonmetal